Steer clear of using Homebase/B&Q, petrol station, kiln dried wood. It burns very hot and fast and is most probably treated with creosote and all kinds of nasty chemicals and is designed to heat and not for cooking. Some of the chemicals could make you ill.
If possible use BBQ wood suppliers. With that type of smoker you want to be using lumpwood charcoal and wood chunks rather than trying to build a full wood fire. the firebox just isn't big enough to support the type of fire you're seeing on the youtube videos and you'll end up swinging temps wildly, constantly opening the firebox to release heat, wasting wood and just generally fighting yourself... Trust me.
Add a few chunks of oak or whatever you choose for the meat you want to smoke to the firebox then put lit coals over the top. maintain temp with coals and add chunks as needed to maintain the wispy blue smoke. If you're doing a long smoke and wrapping for the last part you dont eevn need to use the chunks for the last part, just maintain temp with lumpwood charcoal.
I've used the olive wood and air dried hardwood logs sold in some garden centres, split it up with an axe and used small logs to build an all wood fire with some success but due to the sizes of the logs you need to be adding and watching it constantly.